Circuit breaker



Patented Fes. 23, i937 unirse STATES PATENT otros autres:

olnoUrr Bananen,

Oliver S. Jennings and eld, Ohio, assignors Hiller D. Dorfman, Mansto Westinghouse Eiectric & Manufacturing Company, East Pittsburgh, Pa., a corporation or Pennsylvania anpassen .rune e, i934, serial No. 'izasis s claims.- w1. zoo-isi) Our invention relates to circuit interrupters and particularly to contact structures for circuit` breakes such as' thoseV used with distribution feeder and moderate power network systems.

Circuit breakers for this type of service are subjected to Very severe and exacting requirements. Operation in either direction must be reliable and positive, the breaker must carry the normal line` current without undue 12R. loss, the cost of the breaker must not be excessive, and, perhaps'what is mostimportant of all, the breaker must be capable of quickly interrupting'shortcircuit currents of very large magnitude without damage to the structure of the breaker itself. One arrangement of considerableassistance in meeting these requirements is the provision ofA means for causing 'the circuit breaker contacts 'to open and to close at high speeds, and the principal object ofl this invention is the provision of 'improved means for causing the are forming con- 20 tacts of a circuit interruptor to be separated (or to be closed) attire maximum possible speed.

In the interests of economy, it is highly desirable that the contact structures for breakers ofl thistype be as simple as possible. Despite` this,

25 the contacts must satisfactorily carry the normal overload currents without over-heating or danger of welding. The prior art has found no better speeds, except through answer tothe problem than a' pair of solid mem bers (preferablyV of an are which engage each other with a simple butt contact. Such an arrangement permits high contact pressure with resulting high current capacity and low losses, there is easily broken, and further, the contacts are very inexpensive to manufacture and simple to install. i

Heretofora however, no satisfactory arrange- ,ment' has been known to the art for effecting the separation -of butt type contacts 'at very high the" provision of circuit breaker mechanisms especially designed for ultrahigh-speed operation. of the prior art structures has arisen more or less 45 naturally. Butt .typecontacts are solid and rela- .tively inflexible. Therefore, a spring-or other -resilient means must be interposed betweenthe actu- 'ating mechanism and the contact engaged thereby '50 lto Aassure adequate contact pressure at all times.

Thesespringaif they are to be eective, must bias the contact member (or members) toward the closed-circuit position when the breaker is closed, and in the designs known to the prior art, the eI- iect of the biasing springs -wasto cause the conposition.

'resisting' `material) is little tendency for the contacts to weld together, and even if. they should, the weld This undesirable feature tacts to remain in engagement for a very appreciable periodi of time after the operating mechanism had begun to move toward' the open circuit position.

To /overcome this undesirable characteristic, complicated operating mechanisms were utilized. These mechanisms moved the movable contact member (or members) with sufficient rapidity that, despite the lag resulting from the movement of the contacts toward each other produced by the biasing spring, the desired high-speed operation was effected.

With the structure of our invention butt type contacts are used; The contacts are resiliently biased togetherwhen the breaker is in the closed However,"the separation of the contacts during the opening operation takes place at a speed much greater than has heretoforel been con' sidered'possible in the art. lIn fact the contacts separate more rapidly than they would if they were directly movedb by the operating member itself. Our invention thus not only overcomes the disadvantages of the prior'art, but provides a structure capable of operating in a manner-suverlor even to the optimum mechanism of the prior art.

In addition to the. principal object 'of ou; in-

vention discussed above, it is another object of our. invention to provide a-multi-pole circuit breaker wherein the cooperating contacts for each of the several poles are caused to separate at high speed through the actuation of a single operating which in themselves accomplish the above objects of our invention..4 1

Ciur .invention/is, as mentioned above.. particularly suitable for use with circuit breakers of the type normally used for distribution feeder and moderate power network systems. We shall, therefore, describe fan embodiment of our invention as applied to s devices without, how- ..ever,'in any way tending to restrict the scope,

`each of the three poles.

of our invention except as indicated inthe appended claims.

This preferred embodiment of our invention comprises generally a base of molded insulating material upon which are mounted suitable terminals for each of a plurality of poles, an operating mechanism which includes means for mechanically interconnecting the plurality of switch arms for the several poles ofthe breaker, and a trip device operable upon the occurrence of predetermined conditions to cause the operating mechanism toA open all of the poles of the breaker. Each of the switch arms is provided with a moving contact assemblage which is actuable during the circuit-opening operation to cause high speed .separation of the engaging contacts for each of the poles. The structural features and the details of operation of this embodiment of our invention are particularlypointed out in the appended drawing and specification wherein:

Figs. 1, 2, and 3 are fragmentary views showing the position of one o f the moving contact assemblages and the associated switch arm during the circuit opening operation;

. Fig. 4 is an enlarged fragmentary view showing the features of our improved moving contact assemblage; and, K

Fig. isa sectional View taken on the line V-V of Fig. 1. Y

The main base i, which is of molded insulating materiaL carries strips of conducting material 9k which serve to connect the terminals of the circuit breaker with their respective stationary contacts II. The operating mechanism is supported upon the main base I of the circuit Ibreaker by means of suitable screw fastenings (not shown)A which engage the operating mechanism frame I'i.

A movable switch member I9, which includes a movable contact assemblage 2I and a suitable supporting frame 23 therefor, is provided for These three switch members I9 are mechanically interconnected by means of an insulating tie-bar 25 which extends across all three poles of the breaker. The frame 23 of the central switch' member is pivotally supported o`n the frame I1 of the operating mechanism through a suitable pivot pin. This pivot pin provides a support for the three interconnected switch arms, and thuspermits the single operating mechanism to actuate all three poles of the breaker.

Each of the switch arms I9 comprises,.as mentioned above, a channel-shaped'frame member 23 (Fig. 5), the side portions o f which are joined at one-end by a narrow strip 4I formed integral therewith and at the `other end by a somewhat larger strip 43. A square-opening 45 is formed in each of the spaced side portions of the individual frame members in order to provide a space for the insulating tie-bar 25, this bar being held in position by a suitable plate 41 which .is riveted to the'frame itself by the' rivets 49.

The movable contact assemblage 2| comprises a channel-shaped support frame 53 (Figs. 4 and 5) which is adapted to be pivotally mounted upon the frame 23 of the cooperating switch member I9 by means of a pivot pin 55 which extends through suitable aligned openings in both frames. A conducting strip` 51 of somewhat greater length than the moving contact frame 53 ispositioned beneath the central portion of that member, being rigidly fastened to the frame 53 adjacent its outer end by means of a rivet 58 which also serves as a support for the moving acusar contact member 6I. The conducting strip 51 terminates in a pair of terminal portions 63 each of which is adapted to engage one of the exble shunts 65 utilized for completing the electrical `circuit from the moving contacts 6I to the other terminals of the device. A piece of spring steel 61 having a rounded end portion 69 is positioned beneath the conducting strip 51 and is securely fastened to the frame 5.3 of the contact assemblage by means of the rivet 1I. A coil spring 13 of considerable stiffness is positioned about the pivot pin 55 and is adapted to bias the moving Contact 6I toward the open circuit position at all times. The cooperating contacts II and 6I engage with a simple butt engagement. Each pair of contacts carries the entire line current for one of the poles, and in the preferred structure the contacts are formed of arc resisting material.

The electrical circuit for each of the poles is substantially thev same, Beginning with one terminal the current flows successively through the conducting strip 9, the stationary contact member li, the cooperating moving contact member 6I, the conducting strip 51, the ilexible' substantially the same width as the spring member 61 forming a part of each of the moving contact assemblages 2|, is positioned between the opposed side portions of the frame I1, anda like plate member is similarly positioned with respect .to each of the outer poles of the breaker. These insulating plates are each adapted to engage'the curved portion 69 of one of the springs 61 during the opening and closing movements of the breaker, so as to dene the motion of the moving contacts 6 I In addition, when the circuit breaker is in the closed-circuit position, these plate members 99 are adapted to prow'de a support point for the right-hand end of the moving Contact assemblage which is subjected at that time to three forces. One of these forces is supplied by the operating mechanism to the switch member frame 23. The second of these forces is the contact pressure force which is supplied through the butt engagement of the moving contact member 6I with the fixed contact member I I. And the third of these forces is supplied by 'the'plate members 99 mentioned above. l

'I'he force applied to the switch member frame 23 is substantially xed, as is the movement of that frame by the circuit-breaker operating mechanism. The action of the spring member connection between the operating mechanism and the moving contact members 6I, thereby causing the cooperating contact surfaces to be held in engagement despite any inaccuracies in the mechanism or any wear of the parts. In eiect, when the breaker is closed,v each of the movable contact assemblages 2| comprises a three-force member whichis rigidly supported at one end, resiliently supported at the other end, and held down by a force applied internmediate its ends. The biasing action of the springs '13 is overcome by the operating mech- /anism during each closing operation, and this spring-is practically ineffective in reducing the normal AYcontact pressure. However, as soon as theswitch member frame 2,3 is raised the least amount by the operating mechanism, the biasing springs 13 do become effective and, as. will be pointedoutlater, effect the desired high speed i affixed. to the base.

blages 2i and the associated switch member frame 23, during either the opening (or the closing) operation. Considering the opening operation, the position shown in Fig. l occurs a very short'- timeafter the operatingmechanism begins to open the breaker. Thel first effect of this opening movement is to lift the moving contact assemblage 2i on the switch member frame 23 a slight distance away from the base I breaker. The immediate eii'ect of this movement is to change the movingcontact assemblage from a pivoted member subjected to three forces to a pivoted member subjected to only two forces. The contact assemblage is thus free to rotate under the biasing action of the spring i3, and as a result, the curved portion 69 ofthe spring 61 is held in contact with the cooperating plate 99 y As the opening operation progresses, the moving contact assemblage 2i is progressively moved through the positions shown ,in Figs. 2 and 3, to its fullyopen position where the contacts i land t! have approximately twice the separation shown in Fig. 3.

It is immediately apparent that the result of this is tocause a much more rapid separation of the cooperating contact surfaces than would result if the contact members 6i were moved directly by the switch `member frames 23. It is also apparent that by properly proportioning the dimensions ofthe moving contact structure, the speed of separation of the contacts can be varied f over a wide range. y

This arrangement, which permits the opening of the moving contacts to be effected at high speed, is one of the principal features of our invention, and in'v connection therewith, it is important to note that when the contacts are in .the fully open position the amount of contact separation is greater than could be effected if themoving contacts 6|A were rigidly supported on the switch member frame 23, or if it were sup- :ported by the usual contact pressure-securing spring.' As contrasted with the usual form of contact assemblage, o ur, moving contact members are biased'not to the'closed-circuit position but to the open-circuit position,except when the breaker is in the fully-closed position. At that time a second spring is stressed to provide the desired contact pressure and to provide4 a resilient connection intermediate the operating; mechanism and the contact members themselves.

gravity of the movable contact assemblage 2i is to the right of the pin 55, 'the resulting inertia eifect will, during the opening and the closing of the breaker, produce substantially the same eiect as the yspring 13. With such an arrangement the spring 13 can be made comparatively weak, since its chief function will be the holding of the contact arm in the extreme open-circuit position when the breaker is in the open-circuit I position.

Through the provision oi means whereby the moving contacts are caused to disengage the cooperating stationary contactslat very high speed, which means at the same time produces a greater separtion of the cooperating'contacts than would be possible if the moving contact were rigidly fixed to the associated switch member frame, it is possible to use a much less expensive mechanism for actuating the circuit breaker. This resultsi'roxn of the n shoum also be noted that if the center of i the fact that a moderate speed mechanismV can be utilized for securing high-speed opening of the circuit breaker contacts, and also from the fact that a much greater separation of the contacts thanhas heretofore been considered possible for an operating mechanism of given dimensions is made possible. To summarize, not only does ourvl invention permit the use of a less expensive, slower speed mechanism, but in addition it permits the use of one having smaller physical dimensions than has heretofore been considered possible.

From the foregoing it will be seen that we have provided an improved circuit breaker contact structure which possesses numerous advantages over, and which differ verylmaterially from the structures heretofore known in the art. We have provided a moving contact assemblage whichy `biasing the contacts to the open position, -as

against the usual arrangement 'for biasing the contacts to the closed position, in combination with anauxiliary means for securing the desired contact pressure when the circuit breaker contacts are in thev closed-circuit position, thus permitting the use of the highly desirable type of butt contacts. I Moreover, our improved form of contact structhe cooperating contacts than has heretofore been possible, but in addition it effects a much greater separation of those contacts for a definite movement of the actuating mechanism than. has been known to the prior art.

While in accordance with the patent statutes we have disclosed the foregoing details of a specic embodiment of our invention, and while this improved operation ture not only secures a higher speed opening of n certain of the claims are directed to the details ofv this preferredembcdiment, it is to be understood thatv the principles disclosed are capable of much wider adaptation to the art of circuit interruption generally. We desire, therefore, that the language of our claims shall be accorded the broadest-reasonable construction, and that our inventon shall be limited only by what is expressly stated'therein and by the prior art.

We claim as our invention:

1. In a circuit interrupter; a base member; a' stationary contact means; a switch arm movable to an open and to a closed circuit position; a contact assemblage pivotally mounted on said switch arm; and actuatingmeans for moving said switch arm to open and to close contact assemblage including a contact member which is adapted to engage said stationary contactmeans and whichis positioned at one side of thepivot point of said assemblage, 'a tail portion which is mechanically connected at one end thereof to said contact member and which has a portion positioned at the other side ofthe pivot point Aof Asaid assemblage, and spring means which biases said assemblage for rotation about the said pivot said interrupter; saidV rotate about its axis during the circuit opening operation, in such vmanner that said contact member shall 'be moved away from said stationary conf tact means, during vthe entire opening operation of said swi* ih, ata rateof motion greater than the rate which would result if said contact member were rigidly connected to said switch arm.v

2. I n a circuit interrupter; a base member; a stationary contact member`v iixedly supported thereon; a pivotally mounted switch arm movable to an open and to a closed circuit position; a contact assemblage; means for pivotally supporting said contact assemblage on said switch arm, adjacent thel unpivotect end thereof; and actuating means for rotating said switch arm about its pivot point to open and to close said interrupter; said contact-assemblage including a frame which is engaged by said means for pivotally supporting said assemblage intermediate `the ends thereof,A a movable to the outer end of said frame for cooperating with s aid 'stationary contact member, spring means biasing said frame for rotation in such direction that said movablecontact member is biased away -from said stationary contact member, and a tail portion which is aiiixed at one of its ends to said frame and which has a portion positioned at the inner side ofthe pivot point of said frame, that portion extending along said switch arm a substantial said tailA portion opposite to that which is ai'- fixed to said frame slidably engaging said base member in order to control the movement of said frame and said movable contact member under 'the action of said biasing means during the operation of said interrupter; the dimensions of said tail portion and said frame and the positioning' of thev several pivot and engagement points being so correlated that said movable con# tact member is caused vto disengage said stationary contact member, .during the -entire circuit opening operation, ata rate of motion sub fixedly supported thereon; a pivotally mounted contact member aixed said switch arm -for a distance; Lthe end oi.'

. switch arm,

of resilient stantially greater than the rate of motion which 1 tions of which are .engaged by said support pin intermediate the ends of said auxiliary frame, a .substantially rigid contact member 'aiixed to the outer end of said auxiliary frame for cooperating with said rigid stationary contact member, spring means biasing said auxiliary frame for rotation about said pin in such direction that said movable contact stationary contact member, and a resilient tail portion which is aiiixed atone of its ends to said auxiliary frame and which has a portion positioned at the inner side of the pivot point of said auxiliary frame, that portion extending along substantial distance; the end of said tail portion opposite to that which is aflixed .to said 4auxiliary frame slidably engaging said base member in order to control the movement of said auxiliary frame and said movable contact member supported thereon under the action .of said biasing means during the operation of said interrupter; the dimensions of said resilient tail portion and said auxiliary frame and the' positioning of the several pivot and engagement points being so correlated that said movable contact member moves away from said stationary contact member, during the entire circuit opening operation, at a rate of motion substantially greater than the rate of mo` tion which would result if said movable contact member were rigidly connected to said U-shaped and saidvtail portion being formed material in order thatl said rigid contact members may be resiliently biased into engagement with each other when said inter- -rupter is in the closed circuit position.

OLIVER s. JENNmGs. HILLER D. Donn/LAN.

isbiased away vfrom said 

